The parents were being rowed out to a cutter in rough seas when the rowboat capsized.

"When they recovered the bodies James [the father] had his arms around Isabella [the mother] as if he was trying to hold her up, and they were still embraced together when they were pulled out of the surf," Mr Clayton said.

He said the children were all playing nearby. The eldest daughter, 16-year-old Isabella, had her two-year-old sister, Christina, on her hip watching the rowboat.

Four brothers enlist

By the time war broke out the brothers had spread across the country for work.

Frank and James were in Perth, Cyril was in Sydney, and Edward was in Port Pirie.

"Cyril and Edward joined up very, very early September 1914 and they were in the first intakes of their two regiments," Mr Clayton said.

Cyril was in the 7th Light Horse Regiment, from Sydney, and Edward left from Adelaide on the Ascanius with the 10th Battalion, one of the most famous battalions in Australian military history.

The 10th was among the first infantry units raised for the Australian Imperial Force, so was the first ashore around 4:30am on April 25, 1915 at Gallipoli, and penetrated the furthest inland of any of the Australian troops during the initial fighting.

"[Cyril] was taking gear up to the frontline near Armentieres [in northern France] and a speculative shell came across from the German artillery and blew up his little convoy of horses and equipment and he was killed," Mr Clayton said.

Edward died at Pozieres two months later on July 23, just 15 kilometres away.

"As they left their little hidey hole, which was an old shell hole, a high explosive shell blew overhead and Edward disappeared completely and nothing was found, not even a button," Mr Clayton said.

He said James knew Edward had died when he heard "scuttlebutt" from one battalion to another about who had returned and who had not.

"By the time James is ready to go into battle and it's only a few weeks away, he already knows that all of his brothers are gone and there's a lot of evidence, anecdotal evidence from the family, to say he was in a dreadful state psychologically," Mr Clayton said.

"Nevertheless he attacked with the rest of the men of the 11th Battalion and he was shot and killed by machine gun fire on August 19 [at Pozieres]."